1. Field of the Invention
The present invention generally relates to structures for use in a power driven tool for collecting dust generated by the operation of the tool. More particularly, the present invention relates to a structure for use in a power driven tool for collecting dust generated from a workpiece through a dust collecting passage in which a dust collecting fan is disposed.
2. Description of the Related Art
A typical conventional structure for collecting dust provided in a power driven tool, such as sanding or polishing device, comprises a dust chamber in which a dust collecting fan fitted around the shaft of a motor is disposed, a dust intake passage which is connected with the dust chamber and has an opening adjacent the part of the device where dust is generated, and a dust discharge passage connected with the dust chamber on one end and having on the other end an outlet to which a dust bag or the like is coupled. The dust intake passage, the dust chamber, and the dust discharge passage together form a dust removal passage; dust is drawn in through the intake and delivered into the dust bag connected to the outlet when the fan is rotated by the operation of the motor.
One of the problems of this type of structure is that relatively large space is required in the axial direction of the motor shaft so as to accommodate the connections of the dust intake passage and the dust discharge passage to the dust chamber, thus increasing the width of the entire device. The problem is particularly exacerbated if a commutator motor, which typically includes a commutator and a pair of brush assemblies provided for the commutator, drives the sanding device. In this case, the dust chamber is connected to the dust intake passage and the dust discharge passage on either side of the plane in which the axes of the brush assemblies are disposed. This tends to broaden the axial width of the dust chamber and adversely affect the weight balance of the entire device, thus reducing the operability of the device. If the width of the dust chamber is reduced to maintain the balance of the device, the connections of the dust intake passage and the dust discharge passage to the dust chamber cannot have sufficient cross sections, thus resulting in a reduced airflow through the passage and efficiency in collecting dust.